Method for repairing a transport pipe

ABSTRACT

This describes a method and apparatus for repairing a plastic transport pipe with a defective section while the pipe is under pressure. A pressure vessel encloses the defection section and seals with the pipe. The defective section is cut in two and the defective section drops out into the lower space of the vessel. A repair nipple is then moved into the space between the two cut ends of the pipe. Electrofusion collars are placed over the joint between the insert nipple and the cut ends of the transport pipe. The electrofusion collars are then energized to effect a leakproof joint between the insert nipple and the two ends of the transport pipe. The insert nipple may be any replacement section desired, such as a section with a Tee in it.

This is a divisional application of co-pending application Ser. No.07/970,116 filed Nov. 2, 1992, U.S. Pat. No. 5,280,670.

FIELD OF THE INVENTION

This invention relates to a system for repairing leaks in plastic pipethat carries or transports fluids, such as methane, under pressure.

BACKGROUND OF THE INVENTION

Gas lines or pipes for transporting fluids, such as methane, over aconsiderable distance have been recently made of plastic material. Theplastic material may be polyethylene for example. These polyethylene gaslines work well and are widely used, however, they are subject to havingleaks develop in certain sections. When these leaks occur they must berepaired if the line is to be continued to be used to transport gas.

SUMMARY OF THE INVENTION

This invention includes a method and an apparatus for repairing aplastic transport pipe with a defective section therein while the pipeis under pressure. The pressure may be up to 100 psi or more, forexample. The defective section of the pipe is enclosed by a pressurecontainer or vessel that seals with the pipe.

After the defective section is sealed in the pressure vessel, cuttersthat are maintained within the vessel are used to cut two cuts in thepipe so that the defective section is cut out of the pipe and thesevered section drops into a space within the pressure chamber. Thisleaves a space within the container between two cut ends of theremaining pipe.

A repair nipple has been prepared and has previously been placed in thepressure vessel. The nipple is of a length which is about the same asthe distance between the two cut ends of the pipe remaining. There aretwo electrofusion collars placed over the nipple. The nipple is thenmoved by placing, or positioning, arms until the nipple fits snuglybetween the two ends of the pipe.

Next, the two collars are moved outwardly to fit over the two pointswhere the collar and the transport pipe meet. Thus, each fitting betweenthe nipple and the pipe at each end is covered by a collar. Electricheating wires within each collar are then energized. The cut ends at thetransport pipe are thus fused to the insert nipple.

In some cases it may be desired to insert a Tee into the pipeline toeffect a take off, even though there is no leak in the transport pipe.If that is the situation, a Tee nipple is inserted into a cutout spaceat the desired location and in a manner as described above. The insertedTee would have a valve on the portion of the Tee that is perpendicularto the pipe and any desired replacement fitting may be used.

After the transport pipe has been repaired, the pressure in the vesselis relieved. After the pressure has been relieved the pressure vessel istaken from the pipe. The pipe is then completely repaired. This has beenaccomplished without taking the pressure off the pipeline.

It is an object of this invention to provide a system and method forrepairing a leak in a plastic pipeline while that pipeline is underpressure.

It is a further object of this invention to provide a method andapparatus whereby a fluid "take-off" or other replacement fitting can beinserted into a pipeline while the pipeline is still under pressure.

These and other objects of the invention will be readily apparent and abetter understanding of the invention will be had from the descriptionwhich follows when taken in conjunction with the attached drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified view with most of the top of the top section ofthe pressure vessel cut away to show the main components.

FIG. 2 is a view taken along the line 2--2 of FIG. 1.

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 2.

FIG. 5 is a front elevation of the pressure vessel assembled and showingin dotted outline an inserted pipe repair section.

FIG. 6 is a view taken along the line 6--6 of FIG. 5.

Detailed Description of the Invention

The device of this invention includes a pressure vessel that is used toenclose a defective section, or a section, of a pipe to be removed. Apressure vessel 10 includes a lower portion 12 and an upper portion 14that are placed about the pipe section, and the two sections making upthe upper section and lower section are provided with a seal 16 thatmakes it a pressure vessel.

Seal 16 not only seals the upper and lower portions of the vesseltogether but also provides a seal with the pipe that is to be repaired.As shown in the drawings, bolts 18 holds the upper and lower sectionstogether in a conventional manner.

As shown most clearly in FIG. 6, means for forcing seal 16 against apipe 20 is provided. This includes a pipe clamp hydraulic cylinder 22supported from bottom section 12 and is provided with hydraulic fluidthrough lines 34 and 36 respectively for driving the piston withincylinder 22 in opposite directions. The cylinder is provided with a pin24 connected to the piston in cylinder 22 and fits into notch 38 oflever 26. Lever 26 is pivoted about pivot point 40 that is supportedfrom top section 14. The end opposite the notch of lever 26 is connectedto a stem 30 through pivot 28. Stem 30 is secured to clamp shell 32. Theupward movement of pin 24 causes clamp shell 32 to move downwardly andforces clamp shell 32 tightly against the pipe to retain the pipe withinpressure vessel 10 and prevent leakage at seals 16 and 17. There is alower clamp shell 33 secured to lower section 12. As shown in FIG. 5, asimilar clamp shell system is on the other end of pressure vessel 10.There is also provided a fluid inlet 42 and a fluid outlet 44 onpressure vessel 10 so that once seals 16 are effected, fluid can eitherbe directed into or permitted to escape from the interior of pressurevessel 10 or both valves can be shut.

After the pipe section to be repaired has been fully clamped and sealedwithin pressure vessel 10 the next step is to cut out the desiredportion of the pipe. The means for doing that will next be discussed.This includes two cutting knifes 46, one positioned near each side ofthe pressure vessel. The knifes 46 are within knife guide and clamp 48.Knife guide 48 has a mostly semi-circular shaped portion 50 that whenactivated to its operating position will fit snugly against the pipe. Asecond knife clamp 47 with semicircular portion 51 is also driven bydrive-acting cylinder 52. In other words, the contour of knife portions50 and 51 is essentially the same as that of the pipe that is to be cutin two and when activated serves to hold the pipe in place duringcutting operations.

Before a cutting operation commences, knife guide 48 and knife clamp 47are placed in position so that semi-circular sections 50 and 51 areagainst the pipe to be repaired. This acts as an alignment for knife 46.The means for driving this is hydraulic cylinder 52 having shafts 56 and58. As seen in FIG. 1, double pistons 54 are provided with arms 56 and58 that are connected respectively to guides 47 and 48. There isprovided fluid pressure connections 60 and 62. When fluid pressure isexerted in these two, the pistons are driven such that guide clamps 47and 48 are driven toward the transport pipe. A pressure fitting 54 isprovided so that when fluid under pressure is inserted therein, itcauses the two internal pistons to be driven apart, thereby drivingguide heads 47 and 48 apart and in a direction away from the transportpipe.

When guides 47 and 48 are driven so that sections 50 and 51 clamp thepipe, then the next step is to activate the cutting of the pipe in twoat the two spots indicated by the lateral positions of knifes 46. Thisis accomplished by activating cylinder 64 with guide shaft 49 and powerfluid inlet and outlet 66 and 68 respectively. By activating cylinder 64to drive knife blades 46 along their respective guides the pipe is cutinto in two places. When the two cuts have been completed the cuttingknife is retracted. Also retracted are knife guides 47 and 48. As soonas they are retracted the section of pipe that has been cut out of thepipeline drops by gravity into a lower portion of the pressure vessel.

Now that the defective section has been cut out, the next step is toeffect the repair of or placement of a replacement fitting within thepipe. Means for providing this will next be discussed.

Before pressure vessel 10 was connected together, the replacementsection was positioned on placement arms 70. Means are provided so thatthe placement arm holders can be moved selectively in a directionperpendicular to the pipe being repaired and in an axial motion in whichthe two arms are moved apart. Means for obtaining the perpendicularmotion will next be discussed. This includes a shaft hydraulic cylinder72 that has piston 74 with shaft 76. The shaft 76 is connected tomounting block 78 as shown more clearly in FIG. 2. The mounting block 78is secured to and supports arm hydraulic cylinder 80 that, in turn,supports the fitting placement arms 70. Thus by applying hydraulic fluidpressure through connection 82, the fitting placement arms 10 are driventoward the center of the pressure vessel. The extension of the cylinderis such that when fully extended it causes the axis or center of thereplacement nipple to be aligned with the axis original pipe. Hydrauliccylinder 70 also has a fitting 84. When it is desired to retract thepiston 74 fluid is added to this fitting.

As shown in FIG. 5, arms 70 are also placed adjacent and between fusioncollars 86. Once the fitting or replacement section has been positionedbetween the two cutoff ends, it is necessary to seal the two sections tothe inserted fitting. The two fusion collars 88 are then drivenlaterally by arms 70 until they fit over the joint where the fittingmeets with the cut portion of the pipe as shown in dotted lines of FIG.5.

Referring back to FIG. 1, double acting hydraulic cylinder 94 isprovided with arms 92 and 93 driven by pistons 95 and 97. Rods 92 areconnected to arms 70 and when fluid is injected under pressure throughfittings 98 and 99, the arms are driven to the interior of the cylinderto the position shown in FIG. 1. When power fluid is connected throughfitting 100 arms 92 and 93 are driven outwardly to the positionindicated in FIG. 5. Thus, it is seen that hydraulic cylinder 72 is fordriving arms 70 in a direction perpendicular to the axis of the pipebeing repaired, and cylinder 94 drives the arms either laterally in adirection parallel to the axis of the pipe being repaired. After thepipe has been cut and the cutout section is dropped out of the way,cylinder 72 is activated to drive the replacement fitting into alignmentposition with the pipe. Thereafter cylinder 94 is activated to drive thearms 70 outwardly, pushing collars 86 to the position shown in FIG. 5 sothat they enclose the contacts of the ends of the fitting and the endsof the transport pipe as illustrated in FIG. 5. When this has beenaccomplished, there are provided electrical connections 101 that go to aswitch and power source (not shown) so that, at this time, the operatorcan energize collars 86 and cause the collars to fuse with the transportpipe and the insert fitting or nipple to create a leak proof joint.

If it is desired, one can use inlet conduit and valve 42 and outletconduit and valve 44 to purge the interior of the vessel of the existingair after the pressure vessel has been sealed to the pipe. One mayinject nitrogen and drive out the air so that there is no explosivemixture in the vessel.

After collars 86 have been energized and the pipe and the insert arefused, then pressure can be released from the pressure vessel by openingeither valves 42 and/or 44. Then cylinder 22 is pressurized throughconduit 34 to drive rod 24 away from lever 26. This releases thepressure of clamp shell 32. Then by unbolting bolts 18 the vessel can beseparated from the upper part and the lower part so that it can beremoved from the pipeline. At this time, the replacement section hasbeen effectively placed into the existing pipeline without removing thepressure on the transport pipeline itself.

Although the discussion was centered around repairing a leak in thepipeline this method can also be used to prepare an outlet. In this casethe replacement section or fitting can well be a "T" joint in which thestem of the "T" would be provided with a valve mechanism so that a fluidtake-off fitting can be provided.

The claims and the specification describe the invention presented andthe terms that are employed in the claims draw their meaning from theuse of such terms in the Specification. The same terms employed in theprior art may be broader in meaning than specifically employed herein.Whenever there is a question between the broader definition of suchterms used in the prior art and the more specific use of the termsherein, the more specific meaning is meant.

While the invention has been described with a certain degree ofparticularity it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiments set forth hereinfor purposes of exemplification, but is to be limited only by the scopeof the attached claim or claims, including the full range of equivalencyto which each element thereof is entitled.

What is claimed is:
 1. A method of repairing a transport pipe having aselected section and having fluid therein under pressurecomprising:enclosing the selected section of the pipe in a pressurecontainer; cutting said selected section out of said pipe while saidcontainer is under pressure and leaving a space between cut ends of saidpipe within said container; placing a replacement nipple within saidspace, said nipple supporting two electrofusion collars, said nipplebeing of a length to fit into said space; moving said collars axiallyalong said nipple to fit over the position where said collars and theends of said transport pipe meet; and energizing said collars to fusesaid transport pipe with said nipple to create a leakproof joint.